Anselmo practised as a barrister in Hong Kong from July 1989. He was appointed Senior Counsel in May 2001. As counsel, he had a broad civil practice, specialising in shipping, commercial, company, revenue and telecommunication law cases.

He became a judge of the Court of First Instance on 15 September 2003. As a judge, he heard numerous applications relating to arbitration, including deciding FG Hemisphere at first instance. For a link to the Judgments database of the Hong Kong judiciary, click here. Cases in which Anselmo appeared as counsel and his decisions as judge may be searched by typing in "A. T. Reyes".

Anselmo stepped down from the Hong Kong Judiciary on 14 September 2012 to practice as a commercial arbitrator and advocate in arbitrations.

On 1 October 2012 Anselmo became Professor of Legal Practice at the University of Hong Kong.

He is the author of 2 privately printed books: Reflections on Civil Procedure under Civil Justice Reform and How To Be an Arbitrator: A Personal View. The books are based on lecture series which he delivered in 2009 and 2012 respectively under the sponsorship of the HKMLA and the HKU Faculty of Law.

The English print run of the first book is now exhausted. But it is available in Chinese as Qiantan xin minshi sifa susong (淺談新民事司法訴訟), published by Joint Publishing (HK) Co. Ltd. (JPC) in March 2012.

The English version of the second book was published by the HKMLA in October 2012. It will be available in Chinese as Qiantan zhongcai (淺談仲裁) to be published by JPC in late 2012.